A priority encoder circuit has four inputs, x3,x2,x1,x0. The circuit has three outputs, z,y1,y0. If one of the inputs is 1,z is 1 and y1 and y0 represent a 2-bit, binary number whose value equals the index of the highest numbered input that is 1 . For example, if x2 is 1 and x3 is 0 , then the outputs are z=1 and y1=1 and y0=0. If all inputs are 0,z=0 and y1 and y0 are don't-cares. Build the truth table of the function. ( 3 points)